1. Field of the Invention
This invention relates to an inverter device for converting a D.C. power to A.C. power by switching a MOS transistor to produce the output A.C. power and more particularly, to an inverter device capable of eliminating harmonic components of in-phase mode which are otherwise superposed on an oscillating output voltage.
This invention can be used as a power source for high-frequency discharge pumping CO.sub.2 gas laser devices, high-frequency induction heating furnaces, or the like.
2. Description of the Related Art
Conventionally, an inverter device constructed to convert D.C. power to A.C. power of a desired frequency, using a switching MOS transistor and for output is used as a power source for high-frequency discharge pumping CO.sub.2 gas laser devices and high-frequency induction heating furnaces.
AMOS transistor has a relatively large output capacitor existing between the drain and source thereof. This output capacitor is parasitically created when the transistor is formed and causes a power loss when a high-frequency operation is effected, and further, resonates with the inductance of a wiring to generate harmonics.
These harmonics are transmitted via a stray capacitor between the drain of MOS transistor and the ground and a stray capacitor between the primary and secondary windings of a matching insulating transformer connected between the MOS transistor and the load; i.e., the harmonics are superposed on the output A.C. voltage in the in-phase mode.
As a result, the peak value of a voltage waveform applied between the drain and source of the MOS transistor is raised and the input D.C. voltage level is limited, making it impossible to derive a sufficient output power.